SecurityPkg/SecurityPkg.dsc: Declare PciSegmentLib

SecurityPkg/SecurityPkg.dsc: Declare PciSegmentLib

PiDxeS3BootScriptLib will be updated to consume PciSegmentLib
instead of PciLib to support multiple PCI segment.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Amy Chan <amy.chan@intel.com>
Cc: Chao Zhang <chao.b.zhang@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>